Method and apparatus for transforming crystalline structures of drawn tungsten wires



July 21, 1925. 1,546,899

R. JACOBY METHOD AND APPARATUS FOR TRANSFORMING CRYSTALLINE STRUCTURESOF DRAWN TUNGSTEZN WIRES Filed July 6, 1922 Fly. 1

. I I M I+ 16 Patented July 21, 1925.

UNITED STATES PATENT OFFICE.

RICHARD JACOIBY, F BERLIN, GERMANY, ASSIGNOR T0 GENERAL ELECTRIC COM-PM, A CORPORATION OF NEW YORK.

METHOD AND APPARATUS FOR TRANSFORMING CRYSTALLINE STRUCTURES OF DRAWNTUNGSTEN WIRES.

Application filed July 6,

To all whom it may concern:

Be it known that I, RICHARD JACOBY, a citizen of the German Republic,residing at Berlin, Germany, have invented certain new i and usefulImprovements in Methods and Apparatus for Transforming CrystallineStructures of Drawn Tungsten Wires, of which the following is aspecification.

Although tungsten filaments, which are made by squirting amorphous orfinely crystalline tungsten with a binding medium, can be transformedinto filaments consisting of crystals, each filling the entirecross-section and a considerable length of the filament,

according to a process now known, by passing the'filaments through azone of high temperature, no process is known WhlCh makes it possible totransform drawn tungsten wire into a wire of the same or like Istructure. j

Now it has been demonstrated that at the highest temperatures, onlyslightly below the melting point of tungsten, it possible to convertinto long-crystal wires drawn wires which at somewhat lower temperaturesshow no such tendency. It was however with difficulty that it was foundpossible to keep these temperatures uniform for a wire which was passedin a continuous operation through a zone of incandescence. The reasonfor this lies in the fact that at the highest temperatures the tensilestrength of the tungsten wires is extraordinaril small, so that thewires, by friction on t e contacts even when the latter are as small aspossible, will be broken very easily, and articularly at places whichmay be somew at weaker than the rest. It is a circumstance particularlyfavorable for reaching very high temperatures to have the heatm donewholly or partly by the passage of e ectric current through the wire. Inthis case a somewhat thinner part of the wire, or even a part having alittle greater electrical resistance b reason of excessive'heat at thatpoint, wil become still thinner under the pull exerted,

and thus will melt or break sooner than a part which has not beenweakened. Therefore a wire will melt at a point which is somewhat weakeror is a poorer conductor, without the remaining portions of the wireapproaching, sufliciently near the melting 1922. Serial No. 573,217.

temperature. The disadvantages above described appear more strongly inproportion to the thinness of the wire which is to be brought toincandescence, and in proportion to the speed at which it is drawnthrough the zone of incandescence.

In accordance with the invention, as hereinafter described, the pull onthe wire in .9 the zone of'highest temperature is neutralized to asgreat an extent as desired, or is even replaced by a light pressure. Inthis way it becomes possible to bring the whole wire to temperatureswhich are only slightly: v below the melting oint of tungsten withoutany melting of the thinner parts. It has been demonstrated that thecomparatively slight increase in temperature to just below the meltingpoint of the tungsten which is obtained by means of this inventionfavors the transformation of the short crystals into long crystals, andindeed this is the only thing that makes it possible at all, or thatincreases the speed of the process of crystallization; these points areof the greatest importance as regards the technical application of theprocess.

In accordance with this new process the wire, instead of being drawnthrough the zone of incandescen'ce, as would seem obvious at first witha slender wire, is pressed through it. This is best done by rollerswhich push the wire into the zone of incandescence. Beyond this zone ofincan- 'descence the wire may be caught and passed on, or it may bereceived by a sliding contact or a layer of liquid metal, provided onlythe friction is kept so small that the wire is not bent and cracked inthe zoneof incandescerice. Passing the wire through the zoneOfyincandescence under pressure is facilitated if the incandescentsection of the wire is a'aade as short as possible.

The rollers which push the wire through the zone of incandescence maythemselves form the contacts for the electric current to be sentthroughthe wire, or they may be mounted in mercury which causes the contact, orthey may form the termination of a mercury contact. Other combinationsof the rollers with the contacts are also conceivable.

To facilitate understanding of my invention, reference may be had to theaccompa-nying drawing in which I have illustrated apparatus bymeans ofwhich my invention trical connections of an apparatus in which the wireis moved horizontally.

In the particular arrangement shown in Figure 1 a base 1 carries a metaltrough 2 containing a. body of mercury 3. The metal trough 2 1selectrically connected to one of the leads of a supply circuit 4, theother lead of which is connected to a metal yoke 5' which carriescooperating knife edged contacts 6 made of tungsten or similar highfusing metal and normally pressed toward each other by a weight 7 orsimilar device.

The wire or similar material 8 of which the crystalline structure is tobe transformed is fed vertically upward by any suitable feedingmechanism which will push the wire instead of pulling it, as, forexample, a pair of feedrolls 9 mounted in contact with the mercury 3 anddriven in such a directionthat they push the wire 8 toward the contacts6. The wire 8 between the rolls 9 and the contacts 6 may be heated tovery high incandescence by properly regulating the amount of currentthrou h it. I prefer to provide another pair of Eeed rolls 10 which takehold of the wire as it leaves the hot zone between therolls 9 and thecontacts 6, and to drive these rolls 10 at the same speed and in thesame direction as the feed rolls 9. The entire operation is carried outin a chamber 11 through which inert gas, such as forming gas which is amixture of nitrogen and hydrogen, flows through. the

inlet 12 and outlet 13. By this apparatus the. wire may be pushedthrough the hot zone and a slight pressure exerted upon itlongitudinally due to the frictional resistance offered by the contacts6.

In Figure 2 I have illustrated an arrangement of circuits by which theeffect of gravity on the wire in the hot zone may be neutral ized. Inthis particular arrangement the wire Sis fed by two pairs of feedrolls14 and 15 driven at such relative speeds that a slight end pressureis exerted on the wire in the hot zone between them. A source of directcurrent 16 is connected to the feed rolls so that a current flowsthrough that portion of the wire in the hot zone in the directionindicated by the arrow. To neutralizethe eflect of gravity I mount aconductor .17 parallel to and immediately beneath the hot portion ofthewire 8 and connect it as shown in the drawing so that current from thesource 16 flows through it in the same direction as the current in thewire 8. The mutual repulsionthus set up' neutralizes the effect of Thiseffect may be further supplemented flow of current through it in thatportion.

immediately adjacent to the hot zone is in the opposite direction to thedirection of flow in the hot wire 8 and the mutual attraction thusproduced also tends to neutralize the effect of gravity.

Under specially favorable conditions the process is also capable ofexerting an equalizing effect on the wire, the more'slender portions ofthe wire which become hotter than the rest being pushed together.

In carrying -out the process it may be desirable to carry the wirethrough the hot section in such a manner that even its own weight doesnot exert any pull. This is possible, for example, by passing the wirehorizontally through the zone of highest temperature and therebyneutralizing the efi'ect of gravity on the wire by means of electricalforces. To this end wires having oppositely or like-directed currentsmay be arranged parallel over or under the wire, so that by repulsion orattraction the equalization of weight takes place; but the wire mayalsobe guided perpendicularly, it being forced upward or downward or beingallowed to fall from above against a rubbing contact,

mercury for example, or metal which is kept in a liquid state at quite atemperature.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is,- 1. The process of converting a wire of small crystals ofhigh fusing met-a1 such as tungsten into a wire composed of longercrystals which consists in pushing the w1re to be converted through azone of high tem- 3. In an apparatus for converting a wire composed ofsmall crystals into w1re composed of longer crystals, the combination ofmeans for maintaining a hot zone in which the wire to be converted isheated to a P0111;

only slightly below its melting point, and

feed rolls for pushing the wire to be converted through said zone ofhigh temperature at a speed favorable to the growth of crystalslongitudinally of the wire.

4. In an apparatus for passing a wire through a zone of high temperatureto convert small crystals'into longer crystals, the combination of meansfor maintaining ahot zone, and feed rolls on opposite sides of saidzone, rollers-on one side for pushing the wire through said zone and therollers on the opposite side for receiving it as it leaves said zone.

5. In an apparatus for passing a tungsten wire composed of smallcrystals through a zone of high temperature to pro-- duce longercrystals, the combination of means for maintaining a hot zone, feedingmeans for pushing said wire through said zone, an electrical contact forengaging said wire with some frictional resistance as said Wire leavessaid zone, and means for establishing an electrical circuit through saidcontact and said wire.

- 6. In an apparatus for passing wire through a heated zone to alter itscrystal structure, the combination with means for maintaining a heatedzone, of feed rolls mounted on one side of the heated zone to engage thewire and push it through said heated zone, ,a body of liquid metalforming a contact which engages the wire on the other side of saidheated zone, and means connected to said rolls and to said contact topass current through the wire in said heated zone.

7. In an apparatus for passing wire through a heated zone to alter itscrystal structure, the combination with means for maintaininga heatedzone, feeding means for passing a wire horizontally through said zone,and means for neutralizing the eflect of gravity by electricalattraction or repulsion of the wire in the heated zone.

- 8. In an apparatus for passing wire through a heated zone to alter itscrystal structure, the combination of means for maintaining a hot zone,feeding means for pas tally and for maintaining current of electricitythrough the wire in said zone, current carrying conductors mountedparallel to the wire in said zone and so disposed that the electricalforces between said conductors and said wire will neutralize the effectof gravity on the wire in said zone.

In witness whereof, I have hereunto set my hand this sixteenth day ofJune, 1922.

RICHARD J ACOBY.

g the Wire through said zone horizon-

